Large trailers, such as those used in the freight industries, are equipped with braking systems in order to ensure that the tractor and trailer combination has enough braking power to safely transit on roads. Some trailers are commonly equipped with air brakes that are actuated from the tractor, which air brakes automatically lock the wheels of the trailer when the latter is unhitched.
Smaller trailers, for instance domestic trailers or trailers used to tow recreational vehicles (e.g., boat, motorcycle, ATV, etc.), are seldom provided with a braking system in order to keep their costs low. Accordingly, the braking power is fully supplied by the vehicle towing the trailer. When the trailer is unhitched, random masses (e.g., log, plank, rock) are often wedged behind the wheels of the trailer so as to block movement of the trailer. This action of wedging is hazardous. Moreover, if the operator forgets to wedge a mass behind the wheels, the trailer might start moving if it is on a slope. With the inertia of the trailer and its contents, a moving trailer is hard to stop and may cause severe damages and/or injuries.
Also, some types of smaller trailers may have brake systems. The brake systems may operate with electric, pneumatic, hydraulic networks, among other possibilities. In most cases, the brake systems can only be actuated by actions from the vehicle towing the trailer.